Metal films are used in semiconductor technology to wire together various components formed on a semiconductor wafer. Metal in semiconductor processing can also be used to function as gate electrodes in MOS structures, and as electrodes in thin film capacitors. Elemental aluminum and its alloys have been the traditional metals utilized. Aluminum has emerged as the most important material for such applications because of its low resistivity, superior adhesion to SiO.sub.2, ease of patterning, and high purity.
One technique of metal wiring comprises the patterning and etching of a trough and contact within a thick layer of insulating material, such as SiO.sub.2. Thereafter, a thin layer of a barrier metal, such Ti, TiW or TiN, is provided atop the insulating layer and within the trough and contacts which leads to electrical connection sites which are elevationally lower within the wafer. The barrier metal functions to separate silicon from aluminum which will be deposited subsequently. After barrier metal deposition, a layer of elemental aluminum or an aluminum alloy is deposited to completely fill the trough and contacts. The trough, which was created prior to metal deposition, defines the desired metal patterning such that a planar metal removing technique down to the surface of the insulating layer will leave remaining desired patterned electrically conductive metal lines.
One such planarizing technique is chemical mechanical polishing. When chemical mechanical polishing is used to form metal lines by the above technique, it is referred to as a damascene process. However to date, chemical mechanical polishing of aluminum and its alloys has not been well understood or developed. Accordingly, a need remains for improved chemical mechanical polishing techniques and chemical mechanical polishing slurries for aluminum and its alloys, as well as other materials.